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When comparing a polar and nonpolar molecule with similar molar masses, the polar molecule in general has a higher boiling point, because the dipole–dipole interaction between polar molecules results in stronger intermolecular attractions. One common form of polar interaction is the hydrogen bond, which is also known as the H-bond.
In this approach the local concentration around one central molecule is assumed to be independent from the local composition around another type of molecule. The UNIQUAC model can be considered a second generation activity coefficient because its expression for the excess Gibbs energy consists of an entropy term in addition to an enthalpy term.
Its principal utility is that it provides simple predictions of phase equilibrium based on a single parameter that is readily obtained for most materials. These predictions are often useful for nonpolar and slightly polar (dipole moment < 2 debyes [citation needed]) systems without hydrogen bonding. It has found particular use in predicting ...
The Hildebrand parameter for such non-polar solvents is usually close to the Hansen value. A typical example showing why Hildebrand parameters can be unhelpful is that two solvents, butanol and nitroethane , which have the same Hildebrand parameter, are each incapable of dissolving typical epoxy polymers.
Many of the key molecular players implicated in cell polarity are well conserved. For example, in metazoan cells, the PAR-3/PAR-6/aPKC complex plays a fundamental role in cell polarity. While the biochemical details may vary, some of the core principles such as negative and/or positive feedback between different molecules are common and ...
Electrical potential surface of paracetamol showing polar areas in red and blue. The polar surface area (PSA) or topological polar surface area (TPSA) of a molecule is defined as the surface sum over all polar atoms or molecules, primarily oxygen and nitrogen, also including their attached hydrogen atoms.
Reversed-phase liquid chromatography (RP-LC) is a mode of liquid chromatography in which non-polar stationary phase and polar mobile phases are used for the separation of organic compounds. [1] [2] [3] The vast majority of separations and analyses using high-performance liquid chromatography (HPLC) in recent years are done using the reversed ...
The polarizability of an atom or molecule is defined as the ratio of its induced dipole moment to the local electric field; in a crystalline solid, one considers the dipole moment per unit cell. [1] Note that the local electric field seen by a molecule is generally different from the macroscopic electric field that would be measured externally.